A CME, one type of "solar storm", erupts from the Sun in January 2002. The actual disc of the Sun, indicated by the white circle, is hidden in this view through an instrument called a coronagraph. The coronagraph creates an artificial eclipse by blocking the too-bright light from the Sun's surface, allowing us to view the Sun's dimmer atmosphere.
Click on image for full size Images courtesy SOHO (NASA & ESA). Animation by Windows to the Universe staff (Randy Russell).

Coronal Mass Ejections

"Without warning, the relatively calm solar atmosphere can be torn asunder by sudden outbursts of a scale unknown on Earth. Catastrophic events of incredible energy...stretch up to halfway across the visible solar surface, suddenly and unpredictably open up and expel their contents, defying the Sun's enormous gravity." (Sun, Earth, and Sky by Kenneth R. Lang)

These catastrophic events that the author is speaking about are coronal mass ejections (CME's).

Coronal mass ejections are explosions in the Sun's
corona that spew out solar particles. A lot of material is thrown out into the solar wind. Coronal mass ejections can be dangerous when they hit the Earth.

Coronal mass ejections will become more and more frequent as we near solar maximum. CME's, not discovered until the 1970's, are difficult to detect. That is why we need satellites such as the ACE satellite which acts as a spaceweather station while in orbit. ACE can provide a one-hour advance warning of any geomagnetic storms that would affect the Earth.

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